REACTIVITY AND PHASE EQUILIBRIA OF Y-Ba-Cu-O PARTLY MELTED UNDER ARGON IN NICKEL

Considerable improvement in the processing techniques of superconductors is necessary to control the reactivity of cuprates towards potential substrate materials. In this study, the reactivity of YBa₂Cu₂O_x, melt with nickel was assessed. YBa₂Cu₃O_x was partly melted in nickel at 1080°C under argon. Crystallized compounds indicated that a significant reduction of cuprates occurred due to a low oxygen potential which changes the formal copper valency (Cu₂₊→Cu₊). A substantial nickel contamination of the melt by the attack of the nickel took place with the formation of a nickel oxide skeleton which was selectively infiltrated by a Ba-Cu-O rich liquid. Such a selective mass transport produced a significant chemical demixing and an important modification in the stoichoimetry of the melt. This preferential mass transport, fractional crystallization as well as nickel contamination caused the formation of phases which resulted from an extensive evolution of the compositional path as well as the formation of Ni-doped cuprates.     

基于ATLAS语言的某指示器自动测试程序设计

ATLAS语言的广泛应用在于其以信号为基础,面向测试对象,独立于测试设备等特点,是测试领域通用的用于编写测试程序和描述测试需求的语言.详细介绍了系统的设计过程,利用VC+ +6.0软件编写某指示器的自动测试程序,对该指示器磁航向系统航向精度进行测试并通过ATLAS语言来实现,最后通过GPTS3.0通用自动测试平台和ATLAS语言来实现测试环境搭建及测试结果输出.测试结果表明,基于ATLAS语言的某指示器自动测试程序可以成功得到预期的测试结果.     

Timing During Interruptions in Timing.

Duration and location of breaks in time interval production were manipulated in various conditions of stimulus presentation (Experiments 1-4). Produced intervals shortened and then stabilized as break duration lengthened, suggesting that participants used the break as a preparatory period to restart timing as quickly as possible at the end of the break. This interpretation was supported in Experiment 5, in which similar results were obtained with a reaction time response executed at the end of the break. In all experiments, produced intervals lengthened as the break occurred later during the interval. The authors conclude that varying break location and duration reveal, respectively, the influence of attentional time-sharing before the interruption and of preparatory processes taking place during the break. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adaptive eigendecomposition of data covariance matrices based onfirst-order perturbations

In this paper, new algorithms for adaptive eigendecomposition of time-varying data covariance matrices are presented. The algorithms are based on a first-order perturbation analysis of the rank-one update for covariance matrix estimates with exponential windows. Different assumptions on the eigenvalue structure lead to three distinct algorithms with varying degrees of complexity. A stabilization technique is presented and both issues of initialization and computational complexity are discussed. Computer simulations indicate that the new algorithms can achieve the same performance as a direct approach in which the exact eigendecomposition of the updated sample covariance matrix is obtained at each iteration. Previous algorithms with similar performance require O(LM²) complex operations per iteration, where L and M respectively denote the data vector and signal-subspace dimensions, and involve either some form of Gram-Schmidt orthogonalization or a nonlinear eigenvalue search. The new algorithms have parallel structures, sequential operation counts of order O(LM) or less, and do not involve any of the above steps. One particular algorithm can be used to update the complete signal-subspace eigenstructure in 5LM complex operations. This represents an order of magnitude improvement in computational complexity over existing algorithms with similar performance. Finally, a simplified local convergence analysis of one of the algorithms shows that it is stable and converges in the mean to the true eigendecomposition. The convergence is geometrical and is characterized by a single time constant     

The role of protocols and professional judgement in emergency medical dispatching

The task of evaluating incoming calls to Emergency Medical Services (EMS) systems in order to determine the most appropriate response is performed in many different ways in current EMS systems. At one end of the spectrum, the process is entirely dependent on the judgement of professionals, while at the other end protocols specify the exact questions to be asked and corresponding decisions. This case study describes the experience of the Montreal EMS system, Urgences santé, where professional telephone evaluation performed by nurses since 1981 was replaced by a protocolized system in 1992. During the professional era, there were many attempts to formalize the nurses' decision-making process. These first revealed that professional judgement tended to override decision-support tools that did not allow a flexible processing of the information spontaneously provided by callers. Second, the choice of a single protocol for each call was unnatural for professionals who could spontaneously integrate multiple aspects of a problem in parallel. Third, when protocols were used by professionals, it was a posteriori in order to document their decisions rather than actually support them. Fourth, the use of Artificial Intelligence (AI) methods in order to formalize professional judgement revealed its great complexity, which was confirmed by cognitive analyses of the nurses' decision-making processes. In particular, decisions of not sending EMS resources seemed to be the most difficult. These unsuccessful attempts at formalizing professional judgement led to an evaluation of its performance in terms of results, i.e. to which extent actual decisions minimized errors (both false positives and false negatives) and decision times. A random sample of 1006 calls was collected and the ideal decision was determined by concensus of experts for each call based on the patient's clinical condition. This theoretical decision was considered as a goal standard to which actual decisions were compared. Data analysis revealed that sensitivity of telephone triage (i.e. decision to send EMS resources or not) was almost perfect and specificity was 0.55. The necessary compromise between sensitivity and specificity varied with the types of decisions. Decision times were related to the urgency of the situations, more urgent calls being processed more rapidly. These results were interpreted as representing sophisticated optimization processes in professional judgement. The professional system was replaced by a non-professional protocolized system in 1992. This new system has not yet been formally evaluated in terms of results, but many sources of evidence suggest that it was accompanied by a deterioration of performance. Many contextual factors influence the organization of telephone assessment in EMS systems. This case study suggests that professional judgement may be most useful in contexts where the demand for EMS services often exceeds the availability of resources. On the other hand, protocolized systems may be more appropriate in the absence of such constraints, and where the litigation context prohibits the occurrence of any false negative.     

The use of various buffers in the preparation of human lymphocytes for SEM observation

A study is presented of various buffers utilized in the preparation of human lymphocytes for scanning electron microscopy. Of nineteen different buffers tested, Hanks' balanced salt solution +0·04 mol sucrose appeared most adequate for satisfactory preservation of lymphocyte surface architecture.     

Berberine: A naturally occurring phototoxic alkaloid

The isoquinoline alkaloid berberine, present in nine different plant families was found to be phototoxic to mosquito larvae. In the presence of near UV the LC₅₀ for acute 24-hr toxicity was 8.8 ppm compared to 250 ppm for dark controls. Mosquito larvae that were treated with 10 ppm berberine plus near UV for 24 hr and then transferred to berberine-free water showed decreased larval survival and resulted in a smaller cumulative number of pupae and adults as compared to controls, during a subsequent 4-week development period. Berberine was found to be a singlet O₂ generator in experiments with the chemical trap 2,5-dimethyl furan. A slight increase in chromosome aberrations in Chinese hamster cells was also observed with berberine plus near UV treatment. The significance of the phototoxicity of berberine is discussed in relation to plant-insect relations.